CWE-1174: ASP.NET Misconfiguration: Improper Model Validation

What is ASP.NET Misconfiguration: Improper Model Validation?

• Overview: ASP.NET Misconfiguration: Improper Model Validation refers to the incorrect or absent use of the model validation framework in an ASP.NET application, which can lead to security vulnerabilities by allowing unvalidated input to be processed by the application.

• Exploitation Methods:

• Attackers can exploit this vulnerability by submitting malicious input that is not properly validated, potentially leading to injection attacks or unauthorized data access.
• Common attack patterns include injection of SQL queries, script injection, and providing data that the application is not designed to handle, leading to unexpected behavior.

• Security Impact:

• Direct consequences of successful exploitation include unauthorized data access, data corruption, or application crashes.
• Potential cascading effects might include privilege escalation, further compromise of application components, or exploitation of other vulnerabilities.
• Business impact can involve loss of sensitive data, damage to reputation, legal liabilities, and financial losses due to breaches.

• Prevention Guidelines:

• Specific code-level fixes include ensuring that every model in the ASP.NET application is validated against a set of well-defined rules before processing.
• Security best practices involve regularly reviewing and testing model validation logic, using data annotations or custom validation attributes to enforce constraints.
• Recommended tools and frameworks include using ASP.NET's built-in model validation features, leveraging libraries like FluentValidation for more complex scenarios, and employing automated security testing tools to identify validation gaps.

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Technical Details

Likelihood of Exploit: Not specified

Affected Languages: ASP.NET

Affected Technologies: Not specified

Vulnerable Code Example

ASP.NET Example

using Microsoft.AspNetCore.Mvc;
using MyApp.Models;

namespace MyApp.Controllers
{
    public class HomeController : Controller
    {
        [HttpPost]
        public IActionResult SubmitForm(UserModel user)
        {
            // Vulnerability: No model validation is performed
            // This allows malicious input to be processed without validation
            if (user != null)
            {
                // Directly using user data without validation
                ProcessUserData(user.Name, user.Email);
            }
            return View();
        }

        private void ProcessUserData(string name, string email)
        {
            // Process user data
        }
    }
}

Explanation of Vulnerability

In the vulnerable code example, there is no validation of the UserModel object before processing. This means any input, including potentially malicious data, can be passed to the ProcessUserData method, leading to security risks such as injection attacks.

How to fix ASP.NET Misconfiguration: Improper Model Validation?

Fixed Code Example

using Microsoft.AspNetCore.Mvc;
using MyApp.Models;

namespace MyApp.Controllers
{
    public class HomeController : Controller
    {
        [HttpPost]
        public IActionResult SubmitForm(UserModel user)
        {
            // Fix: Validate the model state before processing
            if (ModelState.IsValid)
            {
                // Safe to process user data after validation
                ProcessUserData(user.Name, user.Email);
            }
            else
            {
                // Provide feedback to the user if validation fails
                return View(user);
            }
            return View();
        }

        private void ProcessUserData(string name, string email)
        {
            // Process user data
        }
    }
}

using System.ComponentModel.DataAnnotations;

namespace MyApp.Models
{
    public class UserModel
    {
        [Required(ErrorMessage = "Name is required")]
        [StringLength(50, ErrorMessage = "Name cannot exceed 50 characters")]
        public string Name { get; set; }

        [Required(ErrorMessage = "Email is required")]
        [EmailAddress(ErrorMessage = "Invalid email format")]
        public string Email { get; set; }
    }
}

Explanation of Fix

In the fixed code example, model validation is implemented using data annotations within the UserModel class. The HomeController now checks ModelState.IsValid before processing the data, ensuring only validated and safe data is used. If validation fails, the user is informed with relevant error messages, enhancing both security and user experience.